Elevated soluble urokinase plasminogen activator receptor (suPAR) predicts mortality in Staphylococcus aureus bacteremia

The soluble form of urokinase-type plasminogen activator receptor (suPAR) is a new inflammatory marker. High suPAR levels have been shown to associate with mortality in cancer and in chronic infections like HIV and tuberculosis, but reports on the role of suPAR in acute bacteremic infections are scarce. To elucidate the role of suPAR in a common bacteremic infection, the serum suPAR levels in 59 patients with Staphylococcus aureus bacteremia (SAB) were measured using the suPARnostic (TM) ELISA assay and associations to 1-month mortality and with deep infection focus were analyzed. On day three, after the first positive blood culture for S. aureus, suPAR levels were higher in 19 fatalities (median 12.3; range 5.7-64.6 ng/mL) than in 40 survivors (median 8.4; range 3.7-17.6 ng/mL, p = 0.002). This difference persisted for 10 days. The presence of deep infection focus was not associated with elevated suPAR levels as compared to patients with no deep infection focus. suPAR was found to be prognostic for mortality in receiver operator characteristic (ROC) curve analysis, which was not observed for serum C-reactive protein (CRP); the area under the curve (AUC) for suPAR was 0.754 (95% confidence interval [CI], 0.615-0.894, p = 0.003) and for CRP, it was 0.596 (95% CI, 0.442-0.750, p = 0.253). The optimal suPAR cut-off value in predicting 1-month mortality was 9.25 ng/mL. In conclusion, our study demonstrates that the new promising biomarker, serum suPAR concentration, was able to predict mortality in SAB.